Application of organic residuals (e.g., biosolids and composts) to soil may provide an effective method for sequestering carbon (C), but the long-term stability of such C is not well known. Two field sites were investigated to characterize soil C status 10 to 15 years after amendment with biosolids and composts. Particulate organic matter (POM) was extracted from soil samples by physical separation methods. Near-edge X-ray absorption fine-structure spectroscopy was used to characterize the organic C in the POM fraction. Near-edge X-ray absorption fine-structure spectra revealed, on average, the presence of O-alkyl C (43%), aromatic C (17%), alkyl C (17%), carboxylic C (11%), and phenolic C (11%) in the POM. The alkyl C/O-alkyl C ratio was within the range of 0.19 to 0.69. The addition of organic residuals maintained higher proportions of alkyl C and aromatic C and lower O-alkyl C in the POM fraction than the control, thus revealing a higher degree of organic C decomposition. The results suggest that the application of organic residuals can increase soil C decomposition and thus improves long-term soil C stability.
1Department of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA. Dr. Jinling Li is corresponding author.
2Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, USA.
Address for correspondence: Dr. Jinling Li, Department of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA. E-mail: email@example.com
Financial Disclosures/Conflicts of Interest: This research was financially supported by the Metropolitan Washington Council of Governments.
Received July 10, 2013.
Accepted for publication October 10, 2013.